I was wondering how high I could turn my fuel pressure up with the stock injectors?

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Founder of the Greater Cincinnati F-Body Association
Greater Cincinnati F-Body Association
1988 Yellow Trans Am GTA
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as far as I know, no matter how high you turn the pressure up, the injectors will only flow a max of 22lb/hr depending on which ones you have, all the extra fuel just goes back to the tank

 

they have a shut off point of 72.50 psi.

 

No, this is incorrect. The injectors rated flow is at a certain pressue. As you increase the pressure, you get more flow.

 

Check out n/a rising rate fuel pressure regulators. They allow you to run near stock fuel pressure and stock injectors for economy under most driving conditions, but can offer a massive fuel flow increase at wot, not to mention the substantial hp gains too! www.cartech.net/

 

Actually, I question the 72.50 PSI limit. I think it is much lower and somewhere between 55-60 psi before they "lock".

Also, that "rising rate fuel pressure regulator" would cause the same problem. I am not sure if you are aware of this, but when we measure PSI, we do this with the vacuum line off to simulate "high load" such as WOT. In typical "part throttle condition", the fuel pressure is considerably lower. In fact, when you increase the fuel pressure with an AFPR, you really just effect the pressure at high load (low vacuum). There is MINIMAL effect with an AFPR at low load (high vacuum).

For that "rising rate FPR" to work, you will need a far better fuel pump than the one in the stock GM cars. Fuel pressure > 50 psi tends to make them have a very short life. And, it is ONLY at high load that this higher pressure exists.

Ditto on the injectors. You will need different injectors that can handle higher fuel pressures without locking (and damaging them).

Lastly, you will need to have an eprom burnt to compensate for all that fuel you will begin dumping at high load (low vacuum). Extra fuel alters all the fuel tables, and if you haven't compensated within the eprom (to let the ECM know that you are getting more fuel). You are just going to run too rich.

Extra fuel is only good IF you need it. Most of the time when I have helped people burn an eprom, extra fuel has seldom been the problem. Generally, getting the right spark curve (without detonation) and LEANING the fuel, as it seems too many people subscribe to this MORE IS BETTER concept.

With fuel, MORE IS BETTER only when you need it. But, you also have to let the ECM know about it or you have "Garbage In = Garbage Out".

Don't get me wrong. I am not completely against the idea of the "rising rate FPR". In fact, I can see some advantages in "power-adder" applications, where they have a need to run "stock" at low/no boost situations, and then need the extra fuel for boost.

It actually solves the problem of having to use excessively large injectors (to ensure your Duty Cycles don't go too high @ WOT/high rpm). The problem with big injectors is that the ECM can only shorten the pulse widths so much, thus making "idle" a problem if your injectors are overly large to handle the "boost" situation.

But you will need a better fuel pump and better injectors to properly use that RRFPR. Plus, you MUST get the eprom's fuel tables dramatically altered for it to work properly. On a basically stock engine, it could cause more problems than it solves. But it does have merit for engines with "power adders" or large N/A motors with radical cams where injector sizing is getting to be a problem.